March 14, 2007
Biomass Plus Hydrogen For All Transportation?
Hydrogen generated by nuclear, wind, or solar electricity could greatly increase the quantity and energy density of liquid fuels made from biomass.
WEST LAFAYETTE, Ind. - Purdue University chemical engineers have proposed a new environmentally friendly process for producing liquid fuels from plant matter - or biomass - potentially available from agricultural and forest waste, providing all of the fuel needed for "the entire U.S. transportation sector."
The new approach modifies conventional methods for producing liquid fuels from biomass by adding hydrogen from a "carbon-free" energy source, such as solar or nuclear power, during a step called gasification. Adding hydrogen during this step suppresses the formation of carbon dioxide and increases the efficiency of the process, making it possible to produce three times the volume of biofuels from the same quantity of biomass, said Rakesh Agrawal, Purdue's Winthrop E. Stone Distinguished Professor of Chemical Engineering.
The researchers are calling their approach a "hybrid hydrogen-carbon process," or H2CAR.
The resulting liquids would be more like gasoline than like ethanol since they'd be more chemically reduced and therefore more energy dense. That would remove one of the big downsides of biomass: ethanol only takes you two thirds as far as gasoline and therefore you have to go to gas stations more often if you burn ethanol.
Agrawal is essentially arguing to use electricity from wind, solar, or nuclear to make liquid fuels.
When conventional methods are used to convert biomass or coal to liquid fuels, 60 percent to 70 percent of the carbon atoms in the starting materials are lost in the process as carbon dioxide, a greenhouse gas, whereas no carbon atoms would be lost using H2CAR, Agrawal said.
"This waste is due to the fact that you are using energy contained in the biomass to drive the entire process," he said. "I'm saying, treat biomass predominantly as a supplier of carbon atoms, not as an energy source."
The use of wind or solar photovoltaics to make liquid fuels rather than to supply electricity to home users would remove a big downside of wind and solar: they do not supply electric power reliably when people want it. On a short winter day with little wind photovoltaics and wind turbines aren't much use.
The use of nuclear electric to make liquid fuels would make nuclear more attractive as well. Nuclear power plants could operate liquid fuel generation plants at night and during the winter when demand for electricity is lower. That would enable nuclear plants to supply more electricity for afternoon peak electric demand periods since the nuclear plants would still have big customers for their electricity to make liquid fuels at night and during the winter.
If this process can be made cost effective (and that's a big if) then it would allow us to keep using high energy density liquid hydrocarbons for transportation while ending our dependence on oil and drastically reducing the net emissions of greenhouse gases.
The other alternative is batteries. This approach combined with pluggable hybrids and a total phase-out of coal in favor of nuclear, solar, and wind for all electricity would together eliminate the need for fossil fuels for transportation and electricity.
I'm very impressed by this idea, especially the way it makes primary energy generation (by nuclear, wind, solar) more economical. The one issue not addressed is the efficiency of converting primary energy to hydrogen.
One could tolerate considerable inefficiency for a couple reasons: portability of liquid fuels, better resource utilization of turn 'em on and run 'em full out nukes and highly variable weather based energy sources, and reduced environmental damage from displaced electricity sources like coal and other fossil fuels.
I just had a chance to look at this paper, and the details are devastating. The authors propose the use of $~40 TRILLION (yes, trillion with a T) in PV panels to generate roughly 10 times annual US electric consumption in order to make 239 billion kg of hydrogen (at roughly one gallon-gasoline-equivalent per kg, equivalent to about 239 billion gallons of gasoline — when total US motor fuel consumption is less than 170 billion gallons/yr) so that the legacy vehicle fleet can be run as before.
It would be vastly cheaper just to go electric. Assuming an average value of $20,000 each, the current US vehicle fleet of ~200 million vehicles could be scrapped wholesale for $~4 trillion. Incremental replacement over time would cost perhaps a few thousand dollars per vehicle, cutting the total cost to well under $1 trillion.
I finished a detailed treatment of this last night; it will appear on The Oil Drum this coming week. I expect that it will appear as H2CAR: Another blind alley.
First off, if we committed to building such a huge amount of photovoltaics we wouldn't spend tens of trillions of dollars on them. After buying the first few hundred billion dollars worth the cost of production would fall so far we'd be down in trillions. After that it'd fall faster.
As for paying to throw away all the old vehicle fleet: We could save a lot of money by just letting old cars gradually get displaced by new vehicles.
As for buying up all the existing vehicles: Your cost estimate understates the problem of doing so for a couple of reasons. First, you'd be forcing people to buy new cars. Second, the big buy-up would drive up the cost of each existing vehicle. Why sell your old car when you would then have to buy a new one - and buy it at a time when the demand for cars is enormous from everyone else buying a new car as well?
Better idea: Convert the old vehicles to electric. There are companies doing this for $20k to $60k now. You can find a recent Christian Science Monitor article about this.
Of course, we need better batteries to do that. I'm all for accelerated batter research. Let us spend a few billion a year on it.
Why on earth would we want to spec trillions of dollars (at even $1/watt, 58000 km² of PV @ 135 W/m² would be about $8 trillion) just to keep burning liquid fuels in internal combustion engines? It doesn't matter how much we could buy down the cost, we'd get the job done for 5-10 times less via other means.
My example of buying all the existing vehicles at once was not a proposal. It was just an illlustration of relative value for money (replacing the vehicles is immensely cheaper than the Purdue researchers' scheme for supplying fuel).
I'm not sure it would pay to convert old vehicles to electric either. But we sure should insist that all vehicles coming off the line past, say, 2013 are plug-in hybrids with a minimum of 20 miles all-electric range. Today's batteries are good enough to get started immediately, even if we have to replace them every 3 years for a while. By 2011 we should have at least two suitable Li-ion chemistries plus one or two carbon-backed lead-acid types available. All it would take is standard dimensions and specifications; with those, anyone could build a vehicle which takes batteries or batteries for a vehicle.
We don't need much research any more. The research has been done, the stuff is moving to pilot stage. What we need is markets big enough to get economies of scale in production. The only thing that can do that is getting product to consumers. The government can do that with incentives and a stiff gas tax.
I do not expect to see a stiff gas tax. But how high do you think a gasoline tax would have to be to cause a migration to pluggable hybrids? I'm thinking gasoline would need to cost at least $5 a gallon given the current level of added costs for hybrids.
As for conversion of existing vehicles: When batteries become cheap enough then the conversion will make sense for higher mileage vehicles. At some point putting in an electric engine with batteries will cost similar to getting a gasoline engine rebuilt.
What will those 2011 or 2012 batteries cost? When do we get to the point where a pluggable with even 20 miles range or a pure electric with 100 miles range costs the same as a regular gasoline engine car today?
Gas prices are going to rise; the question is, who is going to capture the rent for this depleting resource, us or the KSA/OPEC? (The other question is, are we going to act to create a gap between our energy needs and our energy supply, or are we going to be caught in a squeeze as the crashes of Cantarell, Ghawhar and the rest become undeniable? That may be as soon as THIS year.)
I think $3/gallon gas plus word of mouth would be enough to get a migration going. Electricity costs the equivalent of about 75¢/gallon; the pluggable would reap a savings of about $2.25/gallon saved, assuming prices go no higher. A $6000 premium would pay itself back over about 2700 gallons of fuel saved; if the old buggy got 30 MPG, that's 81,000 miles (this falls to ~55,000 miles @ $4.00/gallon). That's probably around the life of the car loan these days. Then it would pay back again in trade-in/resale value. The higher the price of fuel (or if there are supply shortages, ala Ontario) the more attractive they'd be.
The idea of conversions rubs me the wrong way. It would take a big change in public attitudes to undertake the risk of the conversion and possible unrecoverable investment. I'd be happy to be wrong about it, though.
Firefly Energy is claiming Li-ion performance at about 1/5 the price. Per the market price for Li-ion, that would be about 70¢/Wh for Li-ion and thus 14¢/Wh for Firefly's cells. Everything else is going to have to compete with that. You want to go 40 miles at 250 Wh/mile and have 20% reserve, you need a 6.25 kWh pack which will cost under $1000.
The other possibility is that someone makes the investment in manufacturing to bring the Li-ion prices down to a small multiple of the materials cost. Likely this would proceed in parallel with competition from Firefly Energy.
In California we already have gasoline that costs more than $3 per gallon. Check out Ventura California gas prices. It is even more expensive in Santa Barbara. We always have 40, 50, 60 cents higher gasoline than the national average. Check out national gasoline prices and see the regional differences.
Of course, we also have more expensive electricity. We are about 40% of the national average for electricity. What electric price are you basing your 75 cents per gallon equivalent for electicity for transportation?
I'm seeing 30 mpg times 250 wh per mile to be 7.5 kwh for 30 miles. If 10 cents per kwh that's 75 cents. Is that what you are doing?
If Fireflag Energy really can deliver Li-ion batteries that cheap then when the OEMs start selling pluggable hybrids I expect some substantial movement away from gasoline and toward electricity for transportation.
Whoops, I screwed up that calculation. Make that 12.5 kWh, so about $1750 for the battery.
The 75¢/gallon-equivalent came from the CalCars website. That may be assuming off-peak rates.
Last, Firefly Energy is making a carbon-foam-backed lead-acid cell. The carbon backing is immune to attack by H2SO4 (eliminating the corrosion failure mode) and the small size of the spaces in the foam both reduce the diffusion distance and prevent lead sulfate crystals from getting too large to be regenerated (greatly reducing the sulfation failure mode). Eliminating the lead used only for electrical connections reduces the weight by up to 70%. This thing should be much, much bigger than it is. I just hope it gets the attention it deserves.